As a vehicle brake hydraulic controller which is mounted in a four-wheel drive vehicle, a conventional configuration is disclosed in which a locking tendency is determined by calculating a vehicle velocity based on an acceleration which is acquired by an acceleration sensor and obtaining a slip rate through comparison of the vehicle velocity with wheel speeds (Refer to JP-H04-293651-A).
However, in determining on a locking tendency by depending upon an acceleration sensor like the one described in the prior art above, in case a failure, for example, occurs in which an output value from the acceleration sensor is fixed to a certain constant value (hereinafter, referred to as an “off fixing”), it is determined that a vehicle deceleration is not generated even if the driver depresses the brake pedal, resulting in a fear that an ABS (an anti-lock braking system) control erroneously interferes on a high-μ road.